Originally Posted by iSennheiser
Okay as much as I remmeber, the amp that I demo the Hd600/650 in comparison with my FiiO E12 is probably sennheiser's own amplifier because i saw their branding and logo on the amp, the colour is silver, hope this helps.
Be careful about trying to remember, sometimes that doesn't work out as well as we'd like and we end up handing over a lot of money to a happy salesman. Try bringing your own DAP and play specific portions of music that you are familiar with that has sections that challenge different aspects of sound, Then do a quick A/B between them. Got to be quick as auditory memory is a funny thing. You might be surprised at the outcome.
Sometimes people prefer one amp over another because it colors the sound more to their liking. IMO that's some people will get a tube amp that has little feedback (open loop vs. closed loop) and swap in different tubes to get the sound they like best. Perhaps this pursuit brings us joy.